Despite advances in medicine and surgery, congestive heart failure is still the primary cause in the prevalence and mortality of cardiovascular diseases (Cohn, J. N., N. Engl. J. Med. 335, 490-498 (1996)). Myocardial infarction, the main cause of heart failure, will lead to the loss of myocardial tissue and disorders of left ventricular function. Therefore, restoration of scarred cardiac muscle is desirable for the treatment of heart failure. Bone marrow cells have been injected via a needle into the myocardium to stimulate myocardial tissue regrowth (Liu, J. et al., Am. J. Physiol. Heart Circ. Physiol. 287, H501-511 (2004); Reinlib, L. & Field, L., Circulation 101, El 82-187 (2000); Schuster, M. D. et al., Am. J. Physiol. Heart Circ. Physiol. 287, H525-532 (2004); Kocher, A. A. et al., Nat. Med. 7, 430-436 (2001); Bel, A. et al., Circulation 108, II247-252 (2003); Ishida, M. et al., J. Heart Lung Transplant. 23, 436-445 (2004)). However, regenerating tissue with sufficient thickness in the thin scarred area after myocardial infarction has proved to be extremely difficult.
Skeletal myoblasts, fetal myocardial cells, and embryonic stem cells are considered to be sources of transplantable cells for myocardial tissue regeneration (Herreros, J. et al., Eur. Heart. J. 24, 2012-2020 (2003); Skobel, E. et al., Tissue Eng. 10, 849-864 (2004); Hodgson, D. M. et al., Am. J. Physiol. Heart. Circ. Physiol. 287, H471-479 (2004)). However, because the vascular network may not be formed with these cells, a multi-layered tissue cannot be constructed.
Myocardial tissue regeneration by cell transplantation using a hypodermic needle has come to be performed as a mode of therapy in heart failure patients. However, thick myocardial tissue cannot be regenerated using this method. It is believed that a cell sheet with a multilayer structure is necessary for the regeneration of thick myocardial tissue. Recently, Okano et al. developed a cell sheet based on a temperature responsive culture dish. Because an enzyme treatment such as trypsinization is not necessary, this type of cell sheet retains the connection between cells and adhesion proteins (Shimizu, T. et al., Circ. Res. 90, e40-48 (2002); Kushida, A. et al., J. Biomed. Mater. Res. 51, 216-223 (2000); Kushida, A. et al., J. Biomed. Mater. Res. 45, 355-362 (1999); Shimizu, T., Yamato, M., Kikuchi, A. & Okano, T., Tissue Eng. 7, 141-151 (2001); Shimizu, T et al., J. Biomed. Mater. Res. 60, 110-117(2002); Harimoto, M. et al., J. Biomed. Mater. Res. 62, 464-470 (2002)). It was expected that such a cell sheet manufacturing technique would be useful for myocardial tissue regeneration. However, because a vascular network could not be formed with existing cell sheets, the regeneration of tissue with sufficient thickness proved to be extremely difficult (Shimizu, T et al., J. Biomed. Mater. Res. 60, 110-117(2002); Shimizu, T., Yamato, M., Kikuchi, A. & Okano, T., Biomaterials 24, 2309-2316 (2003)).
Mesenchymal stem cells (MSC) are pluripotent somatic stem cells present in bone marrow (Makino, S. et al., J. Clin. Invest. 103, 697-705 (1999); Pittenger, M. F. et al., Science 284, 143-147 (1999)). Mesenchymal stem cells can differentiate not only into osteoblasts, chondrocytes, nerve cells and skeletal muscle cells, but also into vascular endothelial cells (Reyes, M. et al., J. Clin. Invest. 109; 337-346 (2002)), and myocardial cells (Toma, C, Pittenger, M. R, Cahill, K. S., Byrne B. J. & Kessler, P. D., Circulation 105, 93-98 (2002); Wang, J. S. et al., J. Thorac. Cardiovasc. Surg. 120, 999-1005 (2000); Jiang, Y. et al., Nature 41S, 41-49 (2002)). Mesenchymal stem cells differ from hematopoietic cells in that they have adherent nature and can grow easily in culture. Recently, it has been discovered that mesenchymal stem cells can be isolated from adipose tissue (Rangappa, S., Fen, C., Lee, E. H., Bongso, A. & Wei, E. S., Ann. Thorac. Surg. 75, 775-779 (2003); Zuk, P. A. et al., Mol. Biol. Cell. 13, 4279-4295 (2002); Gaustad, K. G., Bequest, A. C., Anderson, B. E., Gerdes, A. M. & Collas, P., Biochem. Biophys. Res. Commun. 314, 420-427 (2004); Planat-Benard, V. et al., Circulation 109, 656-663 (2004)). Because adipose tissue is simply a burden for an obese patient with cardiovascular disease, it will be extremely beneficial from a clinical standpoint if mesenchymal stem cells isolated from the adipose tissue of the patient can be used for regenerative therapy of the disease.